The traditional name of one of the three Magi. This name was connected with the three Magi as early as the 6th C, and evidence that the Magi were an important source for medieval people named some form of Casper is evidence by the high probability in some parts of Europe, particularly Germany, that a man named Casper would have at least one or more brother named Balthasar or Melchior, the other two traditional names.

Spellings in J- and I- were perhaps influenced by similarity to Old Frenchjaspe 'jasper'.